First off, the obvious. If Saul "Canelo" Alvarez does end up fighting Floyd Mayweather Jr. this year, it would add the ultimate resume builder out of any fighter of the past decade. Going forward in his young career, Canelo can always say he fought the best of an era whether he wins or loses the bout.
Another positive to fighting Mayweather is the increased media attention that comes with fighting the sport's most infamous fighter. Alvarez's name will be on every major sports website in addition to sports-oriented TV programs, getting his name out to the casual fans that may not have heard of him. Canelo would be doing his career a favor.
Money is also one of the positives that come out of a Mayweather-involved bout. The man who commands the most money in the sport, Mayweather, means a bigger payday for anyone fighting him, including Alvarez.
Lastly, the biggest positive would come in the scenario that Alvarez defies the odds and is able to beat the undefeated Mayweather. If Canelo could pull off the shocking upset, his career would skyrocket to new heights, setting him up to become the leader of the next generation of superstars in the ring.